The boulder is a glacial erratic. It was ripped off the old Canadian Shield and carried to this location by the glacier during the last ice age. The boulder was deposited when the glacier melted about 11,000 years ago (approximate age - will check detailed age later). There is a second geological process in view: freeze - thaw. Water seeps into tiny cracks in the rock. When water freezes, it expands with a lot of force . That opens the crack a tiny bit. The ice melts during the next summer. The widened crack allows more water to seep in during the next season and the freeze - thaw cycle repeates. Eventually, the freeze - thaw action of water caused one end of the boulder to break off. Interestingly, the amount of lichen growth on the outside of the boulder is equal to that on the sides exposed after the end broke off. Lichen grows very slowly. So, the rock break must have taken place 100's to 1000's of years ago. Aug 14/18, Lake Superior Provincial Park.
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